The present invention relates generally to the field of aircraft navigation. The present invention more particularly relates to the fields of aircraft navigation systems and display features. While the present invention particularly relates to the fields of aircraft navigation systems and display features, applications could also include marine and terrestrial navigation systems.
Current enhanced vision systems (EVS) are being certified to extend certain non-precision and Category I (CAT I) operations through utilization of enhanced vision systems (EVS) as a supplement to natural vision. For example, CAT I conditions, at most, only allow descent to 200 ft. HAT before a go-around decision is made if the airport environment is not visually acquired by the crew. For example, with an EVS equipped and certified aircraft, credit is given for the EVS system, so that, in some conditions, if the crew ‘sees’ the airport environment using the enhanced vision system's output, then the approach can proceed down to 100′ HAT before natural vision must acquire the airport environment in order to continue the approach.
Normally, low visibility operations (such as those described above and provided by EVS) beyond CAT I conditions impose higher demands on the reliability, availability and failure modes of the system being relied upon to perform those operations. These more stringent requirements are typically addressed through system redundancy and/or high design assurance levels. Both solutions come at considerable costs.
What is needed are systems and methods for providing higher EVS/SVS integrity without dramatically increasing costs. Higher integrity may advantageously allow special authorization credit even if the EVS does not meet expensive high design assurance levels.